As photographic cameras have become smaller or more compact, the phenomenon of "red-eye" has become more of a problem. This phenomenon occurs in flash photography and results in a bright red dot aligned with the pupils of the subject's eyes. It has been recognized that the likelihood and severity of this effect increases with decreased flash-to-lens separation of the photographic system. Because of this, the red-eye effect has imposed a substantial problem in attempting to meet the desire in providing more compact cameras.
Various solutions have been attempted, including increasing the camera's flash-to-lens spacing. Flash extenders have been provided for cameras adapted to use flash cubes, and extended or elongated flash lamp units have been provided to reduce this red-eye effect. An example is shown in U.S. Pat. No. 4,855,771 which discloses a compact camera and flash unit, and wherein the flash unit is movable to extend the distance between the camera lens and the flash unit for reducing the red-eye effect.
Other approaches to reducing the red-eye effect have been to provide some form of preliminary light or preflash before the main flash from an electronic flash unit. This usually is a short duration flash, the purpose of which is to cause the size of the subject's pupil to be reduced to thereby reduce this annoying effect. An example system of this nature is disclosed in U.S. Pat. No. 4,285,588. That patent describes that the intensity of the flash light reflected by the retina is reduced significantly because such reflected light intensity varies as the square of the pupil aperture during flash light's entry. The actual size of the red-eye spot on the resulting print is directly proportional to the size of the pupil during exit of the reflected flash light. Thus, it is discussed in that patent that both the size and intensity of the red-eye spot are decreased by reducing the pupil size. Other examples of pre-flash or preparatory flash systems are shown in U.S. Pat. Nos. 3,842,428 and 5,153,632. Other systems include steady or pulsating sources such as a red LED or white bulb.
The systems for reduction of the red-eye effect all require some specific operator action or camera control circuitry. One system of this nature requires the operator to depress the shutter release slightly and hold it for at least one second, although it can be held longer, to provide a preflash or even a short duration illumination of the subject. Other systems include a separate button, usually on the back of the camera, which is pushed to turn on a red-eye reduction light on the front of the camera. Still further systems which are automatic involve internal camera circuitry which, when the shutter button is touched and pushed, illuminates a red-eye reduction light and imposes approximately a one second delay before taking the picture while the red-eye reduction light illuminates the subject. Unfortunately, the subject may change position during this one second delay, e.g., turn her or his head away, such that an undesirable or unusable picture results.
Thus, since at least approximately one second of illumination is necessary to cause the pupils to close down and reduce or eliminate the red-eye effect, all systems either impose a delay automatically, or require the user to carefully push the shutter button partway down and wait approximately one second, or push some other button to provide the red-eye reduction illumination. Unfortunately, the delay imposed automatically by the automatic camera/flash systems creates difficulties in obtaining good pictures, and where control must be exercised by the operator many times the operator does not have a sufficiently gentle touch and pushes the shutter button too far and/or too fast such that a flash picture is taken before the red-eye reduction takes effect. Those cameras that have a separate button that is required to be depressed to activate the red-eye reduction function, require that the operator think about and remember to do so. Needless to say, all of these arrangements are difficult and cumbersome to use reliably.
Additionally, detachable flash units used with the hot shoe of a camera, typically have been relatively tall so as to achieve a fairly large lens-to-flash spacing, also for purposes of red-eye reduction. When the flash unit is attached to the hot shoe of the camera, the combination tends to be relatively bulky in order to achieve this red-eye reduction.